Oregon Gov. John Kitzhaber is currently facing loud calls for his resignation because Cylvia Hayes, his fiancee, stands accused of receiving consulting fees on clean-energy work for the state while advising Kitzhaber on those issues. There are also questions about her disclosures on travel expense and ethics forms.

The Democrat is not the first public official to face legal or public relations problems due to the business dealings of a spouse or loved one. Nepotism is as old as politics, but in the era of the dual-career household, it's sometimes difficult for politicians to keep their official and personal lives separate.

"No matter what level of government, there's a very strong chance that the official in question is going to deal with some issues that touch on the spouse's business," said Jack Pitney, a political scientist at Claremont McKenna College. "From the standpoint of the spouses, what seems totally aboveboard and innocent may look very sketchy to someone else, and that's where people get into trouble."

Just last month, former GOP Gov. Bob McDonnell of Virginia was sentenced to two years in prison for having accepted expensive gifts from a donor while in office. McDonnell's legal strategy consisted largely of trying to blame his wife Maureen for the situation, suggesting that she was volatile and needed counseling. The strategy didn't work.

"There is a tendency to blame the spouse not in office, as we saw with Maureen McDonnell," said Larry Sabato, director of the University of Virginia Center for Politics. "Yet one of the keys to being a successful executive is in being able to say no to the people closest to you—relatives, friends, big donors."

It's probably unrealistic to expect political spouses to do what first ladies in the White House traditionally have done -- give up their careers entirely -- said Anne Weissmann, who directs the watchdog group Citizens for Ethics and Responsibility in Washington (CREW).

"It's likely to be a growing phenomenon because we have more women who have careers in their own right and don't necessarily want to give up their careers when their husband is elected to office," she said.

There have been plenty of examples of politicians having to answer for the purported sins of their spouses. When she ran for vice president in 1984, Democrat Geraldine Ferraro had to endure lots of questions and an epic-length new conference about her developer husband's business dealings and tax returns.

In 2013, former Chicago City Councilwoman Sandi Jackson pleaded guilty to tax fraud in a case that sprang from an investigation of her husband, Congressman Jesse Jackson Jr., who had misused campaign funds for personal use. Other politicians, including former Utah Congresswoman Enid Greene Waldholtz and former Pennsylvania Congresswoman Marjorie Margolies-Mezvinsky, have seen their political careers derailed by the sins of their spouses.

Anyone can be married to a crook, but what makes things especially tricky for politicians is how readily their professional duties and private lives can intersect. Ethics rules -- and certainly the media -- are sometimes as concerned with the appearance of wrongdoing as actual wrongdoing.

"It's something like Hollywood -- who you know can be as important as what you know," said Lara Brown, an expert on political scandals at George Washington University. "In a world where access can greenlight projects or work, it requires even more caution and circumspection for those who are actually in the official office."

Marriages may be complete partnerships, but that often doesn't play well in public life. Bill Clinton did himself no favors when he said back in 1992 that voters were getting "two for the price of one" by electing him and gaining his wife Hillary's talents in the bargain.

Some objected to Hillary Clinton, as an unelected spouse, spearheading his unsuccessful health-care expansion initiative. Both Clintons faced heavy legal bills based on investigations into their real-estate investments and her work for a savings and loan as an attorney in Little Rock while he was governor of Arkansas.

"That's a great example, because the Little Rock legal community isn't vast," Pitney said. "Inevitably, there was going to be some overlap between the work of the governor and the work of the Rose Law Firm," where Hillary Clinton was an attorney.

It's common for politicians to refer to spouses not only as their better half but a wiser head. They are frequently criticized when they put their spouses to work, however.

Anne Gust Brown, a former top executive at the Gap, has kept an office just around the corner from her husband, Democratic Gov. Jerry Brown of California. "She's a damn good lawyer and it turns out she is a very good political operative and strategist," Gov. Brown told The New York Times in 2013.

Chirlane McCray, the wife of New York Mayor Bill De Blasio, has played key advisory roles in his campaign and during his time in office. De Blasio has emphasized that his wife is unpaid, but the fact that she has her own staff drawing six-figure salaries has provided fodder for criticism from the New York press.

(By way of disclosure, while he was mayor of Kansas City, Governing Publisher Mark Funkhouser also drew criticism for his wife's role at City Hall.)

Politics is more transparent than it was prior to Watergate and the subsequent proliferation of disclosure laws and sunshine requirements, said Brown, the George Washington political scientist. "If you go back and look 50 years ago, there were many more deals and many more shenanigans the American public would have been shocked about," she said.

It's appropriate that spouses who play a key role in the office or have business dealings that intersect with governmental contracts receive scrutiny, said Weissmann, the CREW interim executive director. There may be nothing formal that can prevent all instances of spousal patronage.

Most ethics rules don't pertain to spouses. Even if they did, there could be huge loopholes in cases like Kitzhaber's, since the governor is not actually married to Cylvia Hayes.

"In the case of Oregon, to say he was not careful is putting it mildly," Weissmann said.

For politicians who want to remain aboveboard, Pitney has simple, although expensive, advice.

"Three words: Talk to lawyers," he said. "Officials might be loath to spend money on all those billable hours, but what you pay the lawyers is nothing in comparison to what it would cost in case one gets into trouble."